This proposal is a competitive continuation of an ongoing NIMH program project grant, MH-23861. The current thrust of the grant deals with regulation of dopamine systems in the CNS and their interrelationships with other neuroregulators with which dopamine is colocalized or which it may regulate, particularly neuropeptides. It has become clear that understanding the process of interaction between these various neuroregulator systems is relevant to the treatment, and perhaps of the pathogenesis, of severe mental disorders. In recognition of their key interrelated roles, we propose to investigate in a coordinated manner several aspects of the regulation of various components of the dopamine and neuropeptide systems. The specific aims of this program project application include: To elucidate the pre- and post-synaptic neurochemical significance of the coexistence of dopamine with other neuroregulators, particularly neurotensin and CCK, in discrete brain regions using in vivo dialysis and voltammetry. To determine the patterns of peptide processing that are altered by dopamine agonists and antagonists, using the pituitary as a model, through the development of methods allowing simultaneous measurement of families of neuropeptides by mass spectrometry. To further develop and utilize the in situ transcription technique, initially developed with the support of this program project grant, to study the regulatory effects of dopamine on neuropeptide mRNA concentrations and structure. To clone the dopamine D2 receptor and study its regulation using the in situ transcription technique in order to study changes in mechanisms involving that receptor that may be critical to severe mental disorders and their treatment. The application is based on findings and methods developed in past research supported by this NIMH program project. Techniques utilized in this interdisciplinary research include in vivo neuropharmacology, mass spectrometry, analytical neurochemistry, biochemical neuroanatomy, peptide neurobiology, and molecular neurobiology.